A semiconductor resistor, as may be fabricated in an integrated circuit (IC) device, typically comprises a body portion formed of a material having a predetermined resistivity, often stated in units of ohms per square, associated therewith. Electrical connection to the body portion is generally provided by a plurality of metal contacts formed at opposite ends of the resistor body. The contacts at the ends of the resistor body may be connected to metal terminals for providing electrical interconnection with other components and/or structures in the IC device.
Since the metal terminals connected to the contacts at each end of the semiconductor resistor are generally of significantly lower resistance in comparison to the resistance of the resistor body itself, a majority of the current passing through the metal terminals of the resistor flows through an inner row of contacts, which represents a path of least resistance. This unequal current distribution in the semiconductor resistor often results in localized heating and electromigration, particularly in the contact regions of the resistor. Electromigration is a well-known reliability problem which generally involves the movement of atoms in a metal interconnection line due to momentum transfer from conduction electrons. The metal atoms migrate in the direction of current flow and can eventually lead to a complete or partial failure of the metal interconnection line. Electromigration may be due to diffusion in a substrate of the semiconductor material, diffusion in grain boundaries, or diffusion on a surface of the material.
Conventionally, in order to meet certain contact electromigration limit specifications, an IC designer is required to increase a length and/or width of the semiconductor resistor and provide additional rows of contacts. However, increasing the number of rows of contacts does not solve the inherent unequal current distribution problem in the resistor, and thus a majority of the current will continue to flow through an inner row of the contacts. Moreover, increasing the dimensions of the semiconductor resistor undesirably increases the overall area consumed by the IC device.
There exists a need, therefore, for an improved semiconductor resistor arrangement that does not suffer from one or more of the problems exhibited by conventional resistor structures. Furthermore, such an improved semiconductor resistor should be substantially compatible with conventional semiconductor fabrication processes.